Forget UPS. There's no substitute for getting in the car and going to get what you need yourself. Bonus points if it's in a Mercedes-Benz E400 Cabriolet.

There's not much cause to be in Livingston, Tennessee in the middle of the week. Planted at the crossroads of no and where, the little town sits within whiffing distance of the Kentucky border. I'm headed there because the Chevrolet dealer in Livingston is the only one within reach that has a valve cover for a 2002 Duramax, and because a friend of mine cracked his while replacing the injectors on his truck. So that's where we're going, foregoing I-40 for the tumbling climb up the forgotten side of Cumberland Plateau in a 2015 Mercedes-Benz E400 Cabriolet.

I've eyed this route since I moved to Knoxville. The map shows a contorted knot of asphalt that only unwinds after it's sure that's done all it can to try and kill you. Those hairpin switchbacks mean exactly one thing: elevation, and lots of it. The E400 isn't the weapon of choice for this kind of acrobatics, but winter's bleeding into spring and the top goes back. It's good enough for me.

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Mercedes-Benz dropped a new direct-injection, twin-turbo, 3.0-liter V6 engine under the hood for 2015. It's good for 329 horsepower and 354 lb-ft of torque, and rolling down the interstate toward Oak Ridge, it feels properly suited to the task of lugging around this two-ton convertible. Plant your foot, let the thing rev, and it will dispatch an onramp or pass with a big, beautiful pull. Mercedes says the 0-60 mph run takes a little over six seconds. Much of the credit for the hustle goes to the seven-speed automatic, which helps keep the car in the powerband.

2015 Mercedes-Benz E400 Cabriolet

We leave the top up on the interstate as we head for the hills. The insulated canvas keeps the sound of the wind and droning semi tires at bay. The cabin's as quiet as a hard top thanks to that thick cloth top. When we pop off of the four lane and catch a stoplight, I peel the roof back. It's the kind of mechanized display that would give the animatronics gurus at Disney palpitations. It takes just long enough for me to sweat whether or not we'll make it before the light changes, and the drivers around us stare. I can't tell if they're impressed by the techno wizardry or if they're just wondering whose grandmother we carjacked.

2015 Mercedes-Benz E400 Cabriolet

Zach Bowman

The E400 cab looks beautiful, especially in this deep blue metallic paint, but it's the kind of car you expect to see driven by someone with an AARP card and an affinity for dog breeds that begin with the word "toy." I feel more than a little conspicuous whipping through rural Tennessee.

We wind through Oliver Springs and Wartburg, a blue harbinger of warmer weather to come. We hear frogs peeping in their ditches, catch the first of the year's robins sprinting to wing ahead of us, and look for the first green weeping willow buds on their whips. It's a good time to be in this neck of the woods. We turn off on 62, the old Nashville Highway, and begin our climb up the plateau in earnest. Sunlight plinks through the bare-limbed trees around us, landing on the interior. It's just as gorgeous in here as at is out there, with the dark blue and beige leathers playing together.

2015 Mercedes-Benz E400 Cabriolet

Zach Bowman

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The road wakes up as we run further from sea level. The big Mercedes does its best to hustle, but it's clear this car was built to cruise, not brawl. With the roof structure gone, the car's lost plenty of rigidity, and the big A-pillars shake over any uneven pavement. Sport mode brightens the car's eyes a bit by holding gears a bit longer and letting that twin-turbo engine breathe a little harder.

The route turns wicked when we hit state route 85. The narrow two-lane clings to the ridge side, occasionally in vain. The pavement dips and breaks where the earth has let go in the past, sending asphalt, guard rail, and anything else present at the time tumbling into the valley blow. The E400 isn't fazed by the drama. The supple damping absorbs the hellish pavement with the reserved acceptance of a butler who's discovered you've spilled red wine on your pocket dog's cashmere cardigan. Again.

2015 Mercedes-Benz E400 Cabriolet

Zach Bowman

Through the hairpins, the E400 proves itself to be just sharp enough to keep you awake. The seven-speed automatic is best left to its own devices. The shifts are quick enough to stay out of your way so long as you keep your hands off the paddle shifters. Manual mode is largely present for appearances only.

The brakes handle the abuse of bringing the big convertible down from speed for each hairpin, but they're hot by the time the pavement straightens itself. I'd be worried if they weren't.

2015 Mercedes-Benz E400 Cabriolet

Zach Bowman

We grab our valve cover, stop long enough for a quick lunch, and head back towards Knoxville. The old Duramax will be back up and running by this time tomorrow, thanks in no small part to the E400 Cabriolet.